The present disclosure relates to an image forming apparatus for charging a surface of a photoconductor.
Conventionally, a photoconductor including a photoconductive layer having a thickness of ten to several tens of μm and forming a surface for carrying electrostatic latent images is used in an image forming apparatus such as a printer or a copier. In an image forming apparatus using such the photoconductor, a phenomenon called image deletion may occur. The image deletion is a phenomenon in which an image is blurred or the periphery of an image is bled.
The image deletion occurs due to a reduction of surface resistance of the surface of the photoconductor. Specifically, by discharge from a conductive member, discharge products such as nitrate ions and ammonium ions adhere to the surface of the photoconductor. If these discharge products absorb moisture in the air to be ionized, the surface resistance of the photoconductor decreases. Electrostatic latent images formed on the surface of the photoconductor having a reduced surface resistance flows to the periphery to induce a potential drop. In this way, boundaries of the electrostatic latent images become unclear, resulting in the image deletion.
To suppress the occurrence of this image deletion, it is known to arrange a cleaning roller (rubbing roller) for rubbing the surface of the photoconductor in contact with the surface of the photoconductor and perform a refresh process such as when a power supply is turned on in a high-humidity environment. The refresh process is a process of causing the cleaning roller to rub the surface of the photoconductor for a given time by supplying a predetermined amount of toner to the cleaning roller while rotating the cleaning roller at a rotation speed faster than that of the photoconductor. In this way, discharge products adhering to the surface of the photoconductor are known to be actively removed. A timing of performing the refresh process is uniquely determined by humidity around the photoconductor. Further, it is known to change a supply amount of the toner during the refresh process according to temperature and humidity air environments around the photoconductor.